The subject has clear division into head (alpha) and tail (beta) motives. Throughout the fugue, the tail motive (the sixteenth-note pattern) plays the predominant contrapuntal role. The subject concludes on the mediant (^3) shortly before the entry of the answer. The subject's emphasis on the dominant (^5) at the start necessitates a tonal answer, so that the answer's harmony does not pull too far from the tonic (in favor of the dominant). Thus, the entire answer is transposed up a fifth, EXCEPT the first note, which is transposed up a fourth to begin on the tonic instead of the supertonic. A bridge connects the end of the tonal answer with the beginning of the subject statement in the bass in m. 5. What may sound like the beginning of a middle entry in m. 7 lacks the tail motive and is therefore more appropriately labelled as a partial entry. An imperfect authentic cadence in D minor (or a "minor" half-cadence in G minor from a more global perspective) concludes the exposition.
The first instance of invertible counterpoint begins in m. 5, when the order of the countersubject and subject is texturally inverted (from CS on bottom and TA on top in m. 3 to CS on top and S on bottom). This is to be expected in any fugue that has a countersubject. To find the interval of inversion, select any interval formed between the two voices. The first note of the CS is an A, which is a 3rd below the TA's C#. The corresponding interval in the inverted passage (beat 3, m. 5) is, from F# in the S up to D in the CS, is a 6th. The interval of inversion, the sum of the two intervals, therefore, is an octave (3 + 6 - 1 = 8). When statements are slightly varied in the inverted passage, a strange interval sum may result. In such cases, check several different corresponding intervals before labelling the invertible counterpoint. Other instances of invertible counterpoint abound in this fugue.
Before the middle section, which is marked by the first middle entry, is a four-measure episode which serves two roles: (1) to bring the music back to a close in the tonic key (m. 10) and then (2) to modulate to the mediant to begin the middle section. The first statement of a middle entry (subject material in a key other than tonic or dominant) is accompanied by the countersubject. As is common in middle sections, the middle entries enter in various keys and occaisionally in stretto. In general, any passage throughout a fugue lacking a complete statement of the subject is labelled an "episode", except at the end when it is labelled a "codetta" (this fugue has no coda or codetta).
A sequence from mm. 25-27 includes two complete legs, the second one down a third from the previous leg and one measure in length. The third leg begins in m. 27 but varies in beats three and four to set up the half cadence in m. 28.
The final section begins in m. 28 when the subject returns in
the tonic key. A varied countersubject accompanies. When subjects (or middle
entries) enter in stretto, a complete countersubject is unlikely due to
the added contrapuntal restraints. I place such statements in
quotes or parentheses to indicate some modification. The subject in m.
29, for example, contains an inverted tail motive.
